The major objectives of this paper include: 1) developing a novel approach to accurately simulate the material/mechanics conditions of composite structures in seawater; 2) characterizing the impact damage, and the residual compression strength of marine composites as a function of time of seawater exposure; and 3) conducting a combined experimental and numerical investigation of the compression failure of marine composite with impact damage. In this study, a new composite “fish tank” approach was developed. Four E-glass/vinyl ester composite specimens were weakly bonded together and inserted into a polymethyl methacrylate (PMMA) base plate. Only one surface of the composite specimen was exposed to seawater. This surface will be subjected to the drop weight impact, which is very similar to the dynamic failure of ship structures subjected to underwater explosion. The specimens will then be subjected to compression until failure. For the simulation of the compressive failure after impact, finite element method with cohesive element was employed.